Protection against photooxidative injury of tobacco leaves by 2-alkenal reductase. Detoxication of lipid peroxide-derived reactive carbonyls

Plant Physiol. 2005 Dec;139(4):1773-83. doi: 10.1104/pp.105.070391. Epub 2005 Nov 18.

Abstract

Degradation of lipid peroxides leads to the formation of cytotoxic 2-alkenals and oxenes (collectively designated reactive carbonyls). The novel NADPH-dependent oxidoreductase 2-alkenal reductase (AER; EC 1.3.1.74) from Arabidopsis (Arabidopsis thaliana), which is encoded by the gene At5g16970, catalyzes the reduction of the alpha,beta-unsaturated bond of reactive carbonyls, and hence is presumed to function in antioxidative defense in plants. Here we show that Arabidopsis AER (At-AER) has a broad substrate spectrum to biologically relevant reactive carbonyls. Besides 2-alkenals, the enzyme recognized as substrates the lipid peroxide-derived oxenes 9-oxo-octadeca-(10E),(12Z)-dienoic acid and 13-oxo-octadeca-(9E),(11Z)-dienoic acid, as well as the potent genotoxin 4-oxo-(2E)-nonenal, altogether suggesting AER has a key role in the detoxification of reactive carbonyls. To validate this conclusion by in vivo studies, transgenic tobacco (Nicotiana tabacum) plants that had 100- to 250-fold higher AER activity levels than control plants were generated. The engineered plants exhibited significantly less damage from either (1) the exogenously administered 4-hydroxy-(2E)-nonenal, (2) treatment with methyl viologen plus light, or (3) intense light. We further show that the At-AER protein fused with the Aequorea victoria green fluorescent protein localizes in cytosol and the nucleus in Bright-Yellow 2 cells. These results indicate that reactive carbonyls mediate photooxidative injury in leaf cells, and At-AER in the cytosol protects the cells by reducing the alpha,beta-unsaturated bond of the photoproduced reactive carbonyls.

MeSH terms

  • Base Sequence
  • DNA, Plant / genetics
  • Kinetics
  • Lipid Peroxides / metabolism
  • Molecular Sequence Data
  • Oxidative Stress
  • Oxidoreductases / genetics
  • Oxidoreductases / metabolism*
  • Photobiology
  • Plant Leaves / metabolism
  • Plants, Genetically Modified
  • Reactive Oxygen Species / metabolism
  • Substrate Specificity
  • Tobacco / genetics
  • Tobacco / metabolism*
  • Tobacco / radiation effects

Substances

  • DNA, Plant
  • Lipid Peroxides
  • Reactive Oxygen Species
  • Oxidoreductases
  • alpha,beta-ketoalkene reductase

Associated data

  • GENBANK/AY058070
  • GENBANK/AY120718
  • GENBANK/BT022058